1. Field of the Invention
The present invention relates a receiver used in digital video broadcasting and in particular to processing of data and control information in the digital video broadcast.
2. Description of the Related Art
Digital video broadcasting operates in some areas of the world, particularly Europe, according to a standard known as DVB-T2. The DVB-T2 standard describes the second generation baseline transmission system for terrestrial television broadcasting. The specification of the DVB-T2 standard is normalized as ETSI EN 302 755, which specification is incorporated herein by reference in its entirety.
FIGS. 1-4 illustrate various aspects of a conventional DVB-T2 system. FIG. 1 illustrates an exemplary high level block diagram of a system 100 for generation of video signals. FIG. 2 illustrates various coding details associated with processing data streams in Physical Layer Pipes (PLPs) and associated control information L1. FIG. 3 illustrates a high level diagram of an exemplary receiver that includes a tuner 301, an analog to digital converter (ADC) 305, a front end 307, a demodulator 309, an equalizer 311, deinterleavers and forward error correction (FEC) 313 and a dejitter buffer 315. According to the DVB-T2 standard, the data streams treated in the FEC part of the receiver include two different kinds of Physical Layer Pipes (PLPs), namely the Data PLP and Common PLP (if any), plus the Layer 1 signaling (L1), which transports the transmission parameters associated with the PLPs. The Common PLP may contain data that is shared among one or more Data PLPs. Data, Common PLPs and L1 are all encoded using forward error correction (FEC) low density parity codes (LDPC)/BCH, and are multiplexed in time. Both LDPC and BCH are well known error detection and correction schemes.
FIG. 4 illustrates a T2 frame in which control information P1 and P2 are shown to come at the beginning of a T2 frame. The P1 symbol carries S1 and S2 signaling fields. The P1 symbol is mainly used for fast initial band scan to detect the T2 signal, its timing, frequency offset, and FFT-size. The P2 symbol is a pilot symbol located right after P1 in the frame and has the same FFT-size and guard interval as the data symbols. The number of P2 symbols depends on the FFT size. P2 symbols carry L1 signaling information. L1-pre signaling has a fixed size, coding and modulation, and includes basic information about the T2 system as well as information needed to decode the L1-post signaling. L1-post signaling carried in the P2 symbol carries more detailed L1 information about the T2 system and the PLPs.
At the receiver side, decoding of Data PLPs, Common PLPs, and L1 signaling can be considered as asynchronous, as L1 is not time-interleaved, while usually Data and Common PLPs are, but have different time interleaving parameters. Additionally, L1 is decoded before the PLPs of a new DVB-T2 frame can be written into the memory of the time deinterleaver. At the output interface, namely the dejitter buffer, the dejitter buffer may receive the PLPs in burst and the dejitter buffer has to buffer those PLPs in memory in order to be provide a regular (as opposed to jittered) output stream on the MPEG-TS interface. Additional information on these and other aspects of DVB-T2 systems can be found in ETSI EN 302 755.